The present invention relates to an apparatus and method for machining a laminate structure to form selected shapes and, more particularly, to a method for machining conductive structures on substrates to form selected shapes.
Conductive structures on substrates such as thin film circuits are presently in use in high performance, high density systems. These thin film circuits include a substrate or base material upon which conductive structures are deposited. This thin film circuit provides electrical interconnections for components that are electrically connected to the conductive structures. These components that are mounted to the thin film circuit are frequently very large scale integrated circuits (VLSI).
The thin film technology used in the manufacture of these thin film circuits provides relatively short interconnection distance and low interconnection capacitance between integrated components, which enhances the system performance. Thin film technology frequently makes use of multiple layers of thin film conducting material. Thin film conducting layers are separated by dielectric material such as polyimide. Each layer of conducting material is defined using known processes such as a photolithographic process. Thin film processing is generally described in the article entitled "Multichip Modules for High Performance Military Electronics" by T. A. Krinke and D. K. Pai from Electricon '91 proceedings, sponsored by the Electronics Manufacturing Productivity Facility, Indianapolis, Ind., Oct. 22 and 23, 1991, and incorporated herein by reference.
The thin film circuit is frequently mounted to a heat sink which provides mechanical strength and improved thermal conductivity between the substrate and a chassis in which the heat sink is mounted. Alternatively, the thin film circuit can be mounted directly to the chassis.
The chassis in which the thin film circuit is mounted may have a variety of external shapes in order to make optimal use of the space available for a given application. For example, a chassis may have a cylindrical exterior shape or form to make optimal use of a volume within a portion of a missile.
Because the thin film circuits are mounted within the chassis, these thin film circuits must be machined to conform with the interior shape or form of the chassis. One method that has been used for machining these thin film circuits is to saw the thin film circuit using a conventional high speed saw. These saws are frequently equipped with a circular carbide tipped saw blade. However, a major drawback of this sawing technique for machining the thin film circuit is that these saws are best suited for cutting relatively straight edges and are not well suited for cutting relatively small radius arcs or curves. The thin film circuit often must have at least portions thereof machined in relatively small radius arcs or curves.
Other techniques that have been used for machining thin film circuits are ultrasonic or laser techniques. A major drawback of both the ultrasonic and laser machining techniques is that each of these techniques tend to delaminate the thin film circuit. This delamination may be either between polyimide layers or between a polyimide layer and the substrate.
There is an ever present need for methods and apparatus for machining thin film circuits to form nonlinear portions such as relatively small radius arcs or curves therein. This machining should be capable of producing nonlinear sides of the thin film circuit that are free from nicks and delamination.